import java.util.*;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main
{
    public static int n;
    public static int[][] dp = new int[110][110];
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        n = in.nextInt();
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                int x = in.nextInt();
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + x;
            }
        }
        int ret = -127;
        for(int x1 = 1; x1 <= n; x1++) {
            for(int y1 = 1; y1 <= n; y1++) {
                for(int x2 = x1; x2 <= n; x2++) {
                    for(int y2 = y1; y2 <= n; y2++) {
                        ret = Math.max(ret, dp[x2][y2] - dp[x1 - 1][y2] - dp[x2][y1 - 1] + dp[x1 - 1][y1 - 1]);
                    }
                }
            }
        }
        System.out.println(ret);
    }
}
